well lets try to explain

see this. http://ffxiv.gamerescape.com/wiki/Ae...Velveteen_Cowl (in the upper side it say ltem lv 27) while usable lv is 25
while this http://ffxiv.gamerescape.com/wiki/Velveteen_Cowl (in the item it say item lv 27) and usable by a character lv 27 check the stats and you see its more than only 2 item lvls.

and all the gear have this dispresentations.
but easy to think on the item lvl is pink, 2lv higher, green 5 and blue 10-20 ( also based on level of the gear, low lv pink have 0 lv higher. and low lv greens have 1. this change around each 10 lvls. unless pink that have max 2 lvls.)